Purpose

We implemented an application for creating interactive cutaway illustrations of complex 3D Models. Such illustrations can be used in different fields of application including medicine, engineering, and industrial manufacturing. Our application gives the user the possibility to view target geometries that are occluded by other objects. The system cuts all occluder objects so that the user can see the surroundings of the target element too. It is possible to compute the cuts from different viewpoints. Furthermore, the user can select any element in the scene as target element. If one target is not enough, the user can select several targets.

The user can select the kind of cut for every single object in the scene as well. For surrounding structures freeform window cuts work very well. For box like structures or structures the only partially occlude the target box cuts should be used.

Functionality

Before computing the cuts, the user must set up all geometries in a scene. A geometry in the scene needs a MeshCollider script and a CutManager script.

The user can create a new target using the Target script applied to the Main Game Object. A target consists of a name and one or more geometries.

The main work is now done in the Main Script in the Main GameObject. First the user can add one or more cameras to the script. By clicking to �Compute Viewpoints� a viewpoint is generated for each camera. By clicking on the button �SetViewpoint� the viewpoint with the Active Viewpoint Index is set.� Furthermore, the user has to choose the target for the illustration by typing the name of the target into the Target Name field. By clicking the �Set Current Target� button the target is selected.

The next step is to construct the occlusion graph. This is done for each viewpoint in the script. The computation of the graph can be very expensive, therefore it is saved in a local Xml file after the computation. Before creating the occlusion graph, the application loads the graph from the xml if it is already saved.

After the computation of the occlusion graph, the final cut must be performed. This is done by clicking on the next button �Perform cut�.� This computation can take a minute if the geometry is very complex. The result can be seen in the GameView.

By clicking on the �Make Screenshot� Button, a screenshot with a specific name can be saved for the illustration.

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